Metallurgical furnace.



PATENTED AUG. 29, 1905.

G. H. BENJAMIN.

METALLURGICAL FURNACE APPLICATION FILED APR.25. 1903.

' WITNESSESK UNITED STATES PATENT OFFICE.

METALLURGICAL FURNACE.

Specification of Letters Patent.

Patented Aug. 29, 1905.

Application filed April 25,1903. Serial No. 154,277.

To a/LZ whom, it may concern:

Be it known that I, GEORGE HILLARD B EN- JAMIN, a citizen of the UnitedStates, residing at New York city, county and State of New York, haveinvented certain new and useful Improvements in Metallurgical Furnaces,of which the following is a specification.

My invention is especially applicable to furnaces of the type known astank-furnaces and used in melting glass-making materials. It may,however, be used in smelting ores to obtain matte or pig metal and inother corresponding metallurgical operations.

The object of my invention is, primarily, to effect a perfect admixtureof the glass-making materials or the separation of a metal from its ore,and, secondarily, to decrease the cost of operation in carrying intoeffect the manufacture of glass or the separation of a metal from itsore by decreasing the time required to complete the operations ofmelting or separation and to decrease the quantity of fluxing materialsrequired in the operations.

I will describe my improved furnace as employed in the operation of themanufacture of glass, leaving it to be understood that such operationwill be modified when the furnace is used as a smelter of ores.

In the manufacture of glass it has heretofore been the practice to makea mechanical mixture of the glass-making materials to form batch priorto the introduction of such materials into the furnace. This method ofproceeding has in practice been found objectionable owing to thefollowing observed facts:

First, the fluxes employed in glass manufacture---soda-ash and saltcakefuse at a much lower temperature than is the case with lime andsilica. As a result there is produced over the melted glass in thefurnace a liquid. layer which is commonly known as salt water and whichconsists of the fused fluxes and the water of crystallization derivedfrom the fluxes, the lime and the silica. The effect of this layer is tointerpose until such time as the combined water in it is evaporated anon conducting blanket between the flame of the furnace and the sand andlime of the glass batch. Further, by reason of the difference inspecific gravity between the sand, lime, and flux they divide intolayers in the tank of the furnace,and consequently the materials whichshould be in contact are separated and are not brought in contact untilin the process of charging, melting, and withdrawal the materialintroduced into the furnace has been moved toward the gathering end ofthe furnace. This process involves what is known in the art as verticalfining--that is, it is assumed that the sand and lime which normallyfall to the bottom of the furnace are caused to be gradually movedupward into a higher zone in the furnace, this movement being due to thedisplacement of the sand and lime by the heavy combined materialsforming glass gravitating from the highest to the lowest Zone of thefurnace in the movement of the glass-making materials through thefurnace.

Second, the fluxes and lime employed are usually in a more dividedcondition than the silica, which is in the form of sand. These materialsare commonly charged into the furnace by means of a shovel or scoop andfloat on the top of the melted glass in the furnace. \Vhile in thisposition the fine particles of these materials are taken up by theair-currents and gas-flames traversing the furnace and carried out ofthe exit-ports and into the regencrators with the effect of cutting downthe quantity of flux or lime below the proper combining proportions withthe silica, and thus delaying combination of the materials to form glassand also filling and clogging the regenerators, thereby necessitating-toeffect proper fusion of the silicathe introduction of fresh fluxingmaterials and lime and frequent stoppage of the furnace to clear out theregenerators.

Third, owing to the fact, as previously stated, that the glass-makingmaterials distribute themselves in liquid layers within the furnace andare only brought into contact after a certain length of time, it isnecessary either to run the furnace at an exceedingly high temperature,which means rapid destruction of the bottom and sides of the furnace bythe action of the flux upon the furnace-blocks, or the employment ofvery long and deep furnaces, a good windowglass furnace at the presenttime varying in length from seventy to one hundred and ten feet and fromfour to five and one-half feet in depth of tank. Such a furnace, it willbe understood, is costly not only to build but to operate, owing to theimmense loss of heat by radiation from its roof and walls.

Fourth, owing to the fact, as above stated, that the flux and lime arecarried off by the gas-flames, considerably more flux and lime isusually employed than is necessary to comblue with the silica to producethe glass required, and, further, owing to the uncertainty of the amountthat will be combined, it is very diflicult to obtain a uniform product.

Further objections exist, but those mentioned are suflicient to pointout the physical difliculties which are experienced and to illustratethe difference in mode of operation between existing furnaces and thatwhich forms the subject of my invention.

The object of my invention is to overcome the difliculties as stated.

The particular feature of novelty in my improved furnace may be said toconsist in a construction whereby charges consisting of flux, fluxes, ora flux or fluxes with lime, or in case where the furnace is used as asmelting-furnace charges of a flux, fluxes alone or combined with carbonmay be introduced into the material to be acted upon L 0., into the sandor ore at successive points in its line of travel from the place wheresuch material is charged into the furnace until it reaches the tank ofthe furnace, and, further, in providing means whereby such basicmaterials will flow or move from the introduction-point to the tank as athin stream or body, and whereby light materials in the form of flux,fluxes, or carbon are not subjected at the time of their introductioninto the furnace to the carrying action of flames or air-currents ontheir way to the exit-flue from the furnace. My invention furtherinvolves various features of construction, which will be pointed out andspecifically claimed.

The accompanying drawings, which may be considered as partiallydiagrammatic, will serve to illustrate the general features ofconstruction of my improved furnace.

Figure 1 is a vertical section. Fig. 2 is a transverse section on theline a a of Fig. 1.

In the drawings, 5 indicates a tank-furnace of the usualconstructionthat is, provided with a tank 6, high crown 7, and cave 8under the tank. Preferably the tank is circular. 1 do not limit myselfin an ywise to the shape of the tank. Extending from one side of thetank and in an upward direction as a series of communicating inclinedand vertical passages is a flue or passage 9. This passage serves topermit the products of combustion and surplus heat from the furnace 5and other heated parts to flow in an upward direction to thechimney-flue 10, or, if desired, through suitable air or gasregenerators, when such regenerators are employed. Under ordinarycircumstances 1 do not make use of such regenerators. The passage orflue 9 is divided into two sets of passagesrl. 0., the passage 11, overand through which the materials under treatment flow or move, to befinally discharged into the tank 6, and the passage 12, which formsby-paths for the products of combustion flowing to the chimney-flue 10.The purposes of these by-path passages will be described later on.

Situated at the top of the flue or passage 10 is a hopper 13, inthelower end of which is a feed-drum 1 1. In the manufacture of glass sandis introduced into the flue 9 through this hopper and falls, asindicated by the dotted line, upon the inclined hearth or floor 15.Located at the lower end of the hearth 15 is a vertical passage 16,which forms a part of the passage 11. Arranged transversely andprojecting inward from opposite sides of this passage are electrodes 17.Two pairs of electrodes are shown. I do not limit myself in anywise tothe number of pairs of electrodes. Immediately under the lower orificeof the passage 16 is a second inclined hearth 15, having its inclinationdownward in a direction opposite to that of the hearth 15, and at thelower end of this hearth is a second passage 16, similar to the passage16. having the electrodes 17, and under this passage a third inclinedhearth 15 inclined downward in a direction opposite to 15, and at thebottom of this hearth is a third passage 16", containing electrodes 17".Under the bottom of this passage is a fourth inclined hearth 15", whichcommunicates at its lower end with the cavity of the furnace 5.

I have shown in the drawings four inclined hearths and three sets ofelectrodes. 1 do not limit myself to the above number of hearths or setsof electrodes, as the number may be increased or diminished. Preferably,however whatever may be the number of the inclined hearths the generalrelation of the hearths as regards their inclination relative to eachother should be maintained. The object of inclining the hearths relativeto each other is, in effect, to reverse the exposed surface of thematerial flowing down the hearths as they flow from one hearth to thenext.

Mounted over the hearths 15 15 .15", and preferably near to their lowerends, are the hoppers 18 18 18", and in the bottom of these hoppers arefeed-drums 19. It will be observed that these hoppers are situated overand approximately at the center of the bypath flues 12. The fluxingmaterials, lime, &c., are introduced through these 'hoppcrs, and thematerial passed through them is de posited upon the surface of thematerial passing over the hearths 15 15 15" immediately prior to theentranceofsuch material into the passages 16 16 16, and thereforeimmediately prior to the time when the combined materials /I. 0., thesand, fluxes, lime, carbonare brought into the influence of the electricarcs formed between the electrodes 17 17 17'.

The purpose of the by-paths 12 will now be understood, which is to carrythe outgoing products of combustion, heat, Sac, around the points ofdeposition of the fluxes, lime, carbon, &c., on the surface of thematerial upon the inclined hearths, and thus prevent the outgoingcurrents from picking up and body of partially-fluxed lime and sand.

carrying off the finely-divided particles of soda, lime, carbon, &c.

The heating of the furnace is accomplished through the instrumentalityof the hydrocarbon-burners 20. Such burners are shown as introducedthrough the roof 7 of the furnace and at various points along the flueor passage 9. I do not limit myself to the disposition shown for suchburners or their number. A suflicient number should be employed tocreate the required temperature and preferably disposed as to directtheir flames not to impact upon the walls of or the materials in thetank or fines, but to permit free development of flame, and thus heat byradiation.

The mode of operation of my improved furnace is as follows: Sa'ndisintroduced into the hopper 13. If desired, this sand may have mixedwith it a small percentage of lime, soda, salt cake, or other fluxingmaterial. Preferably but smallquantities of these materials should beincorporated with the sand. The sand under the action of the feeddrum 14is thrown on thehearth 15 and gradually works its way down the hearth 15toward the electric arcs 17. I have shown no means other than thegravital action of the sand for moving it along this hearth. Hanifestlyany well-known means such as a reciprocating rake, chain traveler, orother devicemay be employed. In practice I find that if the inclinationof the hearth is suflicient the slightlyfluxed sand will flow bygravity, while on the hearth 15 the preliminary heating of the sand isefl ected. This thoroughly dries the sand, drives off a portion of thewater of crystallization, and produces a partial combination between thesand and the fluxes, lime,&c. The partially-fluxed sand and lime coverthe surface of the hearth and first form a silicious coating, which isheld in position by the chill imparted to it by the cooled hearth, andthus serves to protect the hearth from the scoring action of the fluxes.When the partially fluxed and melted sand and lime not held on thehearth reach the lower portion of the hearth, a definite quantity ofdivided flux, lime, &c., is introduced through the hopper 18 anddeposited upon the surface of the moving stream or The stream or body inits movement downward then moves or falls through the electric arcs 17and while passing these arcs is subjected to a very high temperature-@'.6., a temperature considerably higher than can be obtained in any typeof metallurgical furnace heatedby fuel or gas. The effect of thetemperature of the arcs is to produce an intimate combination betweenthe bodies passing through it which fall upon the hearth 15. As thestream or body passes along this hearth a second charge of the fluxingmaterials-lime, carbon, &c. is charged upon the opposite surface of thestream or. body, which is again transmitted through a series of arcs inthe passage 16,

thence onto the hearth 15", through the arcs 17 onto the hearth 15,thence into the tank. WVhen delivered in the tank, the materials are ina perfectly-combined condition. Consequently the size of the tank may beonly such as may be necessary to hold the required quantity of glass toaccommodate the number of blowers employed, as no vertical fining orfurther combination of the materials is effected within the tank. thetemperature of the tank can be controlled to effect the required planingof the glass 71. 6., bringing the glass to the required tenacity ordegree of fluidity necessary for blowing, casting, &c. When the furnaceis used as a smelting-furnace, it is necessarily provided with slag andmetal spouts.

It will be observed that the products of combustion and heat rising fromthe tank do not pass through the passages 16 16 16 on the way to thechimney-flue, but through passage 9 and by-paths 12 around the arcs andaround the points of entrance of the fluxes, &c., and, further, that thetemperature of the flue or passage 9 from the point of entrance of thesand or partially-fluid materials through the hopper 13 to the point ofdischarge into the tank is a gradually-increasing one, which is thecondition desired in practice to obtain the best results.

In the manufacture of glass the employment of an electric arc or arcs asdescribed is desirable, but not essential. It or they may be dispensedwith, as the heat required to effect combination of the materials may beotherwise obtained. In the separation of a metal from its ores they arenecessary to obtain the best results, as the temperatures which can beobtained in the furnace without their use are not sufiicient to producethe requisite combination between the ore-body, the fluxes, carbon, &c.,introduced.

As before stated, I do not limit myself in any wise to the particularfeatures of construction of the furnace shown, as the drawings are onlyintended to illustrate the general features of construction and theprinciple of operation involved in the furnace c'. 6., successiveintroduction of fluxing or flux and lime charges upon opposite surfacesof the material treated, preferably at points of quiescent atmosphere,and, if desired, the treatment of the fluxed material immediately afterfluxing by the high temperature of an electric arc.

The practical effect of the furnace described is a large reduction ofthe fluxing materialslime, carbon, &c.very rapid combination of thematerials, and finally the production of glass of uniform quality or,where an ore is treated, of matte or metal.

Having thus described my invention, I claim* 1. A metallurgical furnaceembodying in its construction, a series of inclined and connectedhearths, means for introducing the mate- It will be understood that rialto be acted on upon the uppermost hearth, means for depositing upon themoving material at successive points along its line of travel, fluxes orother combining bodies, a tank-furnace connected to the lowermosthearth, and means for heating said furnace and hearths.

2. A metallurgical furnace embodying in its construction, a heatedpassage through which the material to be acted on is moved, means forcharging onto said moving material at different points in its line oftravel successive charges of fluxes or other combining bodies, and meansfor diverting the ascending heated currents in said passage around thepoints Where such charges are delivered upon the moving body.

3. A metallurgical furnace embodying in its.

construction, a passage through which the material to be acted upon ismoved, means for heating such passage, means disposed along such passagethrough which charges of fluxes or other combining bodies may besuccessively delivered upon the moving materiahand means situated inadvance of said last-named means adapted to subject the moving materialafter each charge has been delivered upon it to the physical effects ofan electric are.

4. A metallurgical furnace embodying in its construction, a series ofoppositely-inclined connected hearths, means for feeding the material tobe acted on upon the upper end of the uppermost hearth, and means fordischarging upon one surface of the material as it passes over onehearth and upon the opposite surface of the material as it passes overthe succeeding hearth charges of fluxes or other combining materials.

5. A metallurgical furnace embodying in its construction, a series ofoppositely-inclined connected hearths, means for feeding the material tobe acted on upon the uppermost of said hearths, means for dischargingupon successively-opposite surfaces of said material passing over saidhearths, successive charges of fluxes or other combining materials, and

.means for subjecting the material after the introduction of eachfluxing or combining charge to the temperature action of an electricare.

6. A metallurgical furnace embodying in its construction, a series ofoppositely-inchned and connected hearths, means for introducing thematerial to be acted on upon the uppermost hearth, means for depositingupon successive surfaces of the moving material successive charges offluxes or other combining bodies, a tank-furnace connected to thelowermost hearth, an exit-flue connected to the uppermost hearth, andmeans for heating said furnace and hearths.

7. A metallurgical furnace embodying in its construction, a series ofoppositely-inclined and connected hearths, means for introducing thematerial to be acted on upon the uppermost hearth, means for depositingupon successive surfaces of the moving material successive charges offluxes or other combining bodies, means for subjecting the material inits passage from one hearth to the next to the temperature action of anelectric are, a tankfurnace connected to the lowermost hearth, anexit-flue connected to the uppermost hearth, and means for heating saidfurnace and hearths.

8. A n'ietallurgical furnace embodying in its construction, a series ofoppositely-inclined and connected chambers, a passage introduced betweeneach pair of chambers, electrodes in said passages, a passage connectingeach chamber whereby the products of combustion and heated gas will becarried around the passages containing the electrodes.

9. A metallurgical furnace embodying in its construction, a series ofoppositely-inclined and connected chambers, a passage introduced betweeneach pair of chambers, electrodes in said passages, a passage connectingeach chamber whereby the products of combustion and heated gas will becarried around the passages containing the electrodes, a tank-furnaceconnected to thelowermost of said chambers, and an exit-flue connectedto the uppermost of said chambers.

10. In a metallurgical furnace, the combination with a receiving vessel,of means whereby the material to be acted on is caused to move as a thinbody over a series of oppositely-inclined hearths, means for depositingupon the surface of said moving material at different points in its lineof travel, definite charges of fluxes or other combining material, andmeans for heating the materials and fluxes.

11. In a metallurgical furnace, the combination with a receiving vessel,of means whereby the material to be acted on is caused to move as a thinbody over a series of inclined hearths, means for depositing upon thesurface of said moving material at dili'erent points in its line oftravel, definite charges of fluxes or other combining material, andmeans for heating said moving material between each introduction of thecharge to approximately the temperature of an electric are.

12. In a metallurgical furnace, the combination with a receiving vessel,of means whereby the material to be acted on is caused to move as a thinbody over a series of inclined hearths, means for depositing upon thesurface of said moving material at different points in its line oftravel and in a quiescent atmosphere, definite charges of fluxes orother combining material.

13. A metallurgical furnace embodying in its construction, a series ofoppositely-inclined and connected hearths, means for feeding thematerial to be acted on upon the uppermost of said hearths., means forcharging fluxes or other combining materials onto the surface of thematerial as it passes over each hearth,

and means for subjecting said material to a acted upon to a temperaturehigher than that high temperature as it passes from one hearth in thechamber as it passes from one chamber to the next. to the next.

14. A metallurgical furnace embodying in In testimony whereof I afiix mysignature in 5 its construction, a series of inclined, heated thepresence of two Witnesses.

and connected chambers, means for feeding the material to be acted uponinto the upper- BENJAMIN most chamber, means for fiuxing the mate-Witnesses:

rial acted on as it passes through each cham- J. E. PEARSON,

10 her, and means for subjecting the material FRANK OCoNNoR.

